Metallurgical process



Mar. 3, 1925.

W. E. GREENAWALT METALLURGICAL PROCESS Original Filed March 19, 1915 INVENTOR.

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d frequently suggested,in theextraction Patented Mar. 3, 1925.

: .wrnLrnM El GREEN-AWAL'I, or nnnvnn, ooil'oRADo.

I METALLURGICAL r noonss 'i 1921. Serial No. 486,904.

Toall whcm it may concern.

Be it known that I, l/VILLIAM E. Gamma- K wAL aFcit-i/en of the United States, residin 'n tl'recityand county ofDeuver and Statei'ot Colorado, have invented cert-am new "and useful} Improvements in 'MetallurgicatProcess'e's, of which the following. 1s a specification. v

, l'lie inyention will be described more particulai-lyiin reference .to the treatment of copper oi'es, altho it. applicable to other metals.- f It will be described more part1cularly inreference to sulphate solutions, altho it is also applicable to chloride and other shlutions. v I J The subject matter of this application is similar to that oh my co-pending applications, Serial No. 15,583, filed March 19, 19135, Serial No. 228,952,, filed Apr l 116, 1918; and Serial No. 239,255, filed June 10, 1918, or Patents No. 1,340,826, u 1,4 0,059; and Noj1,3 57,495, respectively.

In the extraction of copper from its ores. with dilute acid solutions iron is inevitably dissolved with the copper. .In the electrolytic deposition of the copper from leach solutions containing iron, ferrous iron isnot particularly harin'tul; it mayv be decidedly beneficial. "Ferric iron .is very detrimental; itattacks't-he deposited copper and causes a lossjoi' ellicienov practically in proportion to, the ferric iron in the electrolyte. On the ,other hand, ferric salt hasbeen largely used,

of copper from ilsores. 'It makes a fairly cilicient solvent. One of the objections to its use has been the diiiiculty andexpense of its production andregeneration. It acts beneficially in the extraction of the copper from its ores. It acts harmtully in the precipitation of the copper from its solutions, So far as I know it is, and has been, the custom, without exception, in the'electrolytic deposition oi copper from leach solutions to maintain the ferric iron in the electrolyte at a certain low standard by diverting, or dis carding, a portion of the solution, and after precipitating the copper with metalllc iron, wasting the diverted solution. It 18 one of the objects of this process to turn this d1-.

verted solution, presumably high in iron, to

profitable account.

Renewed August 25, 1923.

In the present process the object is to carry a fairly high iron content in the elec electrolyte,. in the deposition of the copper, V

and regulate its flow thru the cells ,in such a way, that while the ironcontent may be high, only a comparatively small portion,

say, from 0.1% to 0.25% will be oxidized to the ferric condition. This may be done by alternately passing the electrolyte thru a number of cells in multiple, and thru reducing units, at. such a rate that the solution issuing from the reducerswill be practically completely reduced, and the solution issuing from the cells will notexceed 0.25% ferric iron. Ultimately, of course, the iron will accumulate in such amounts in the electro lytethat elimination of part of it becomes 3 desirable, but instead of discarding the solution heavily chargedwith iron salts by precipitating its copper content with metallic iron and then Wasting the solution, I use both the precipitate and the solution to advantage, as I will now describe.

Most leachable ores contain some sulphides as well as oxides. These sulphides, especiallyin disseminated deposits, are usually in the form of chalcocite and chalcopyritc.

.Copper in its oxide (including carbonate) combinations is readily soluble in dilute acids, but the sulphides remain practically unaffected. The result is, that the extraction, under the conditions of ordinary dilute acid leachmg, 1s low and unsatisfactory, and

does not represent the ultimate possibilities ,ofuthe process. While the copper in its sulphide combinations is practically unaffected.

byjsulphuric acid, it is readily made soluble in a dilute acid solution of ferric salts, and

a veryhigh extraction of the copper is salts, from both its oxide and sulphide comobtainable with an acid solution of. ferric binatio'ns. Tov attempt the regeneration of the ferric salts during the electrodepost,

tion of the copper, to a usefuldegree, is difficult, if not im. racticala So far it has proved impractica. The eflicient elecfiolytic deposition of the copper, and, the efli- -cient regeneration and accumulation oflgpge quantities of ferric salts tor leaching, are "diametrically opposed. This was the idea When the electrolyte becomes ,too heavily charged with iron for effective use, a portion is diverted, after the copper electrolysis, to another set of cells, in which the solution high in iron is clectrolyzed under oxidizing conditions, and then the acid ferric salt solution is applied to the ore as a wash and to extract the copper from the ore in its sulphide combinations. The copper so extracted is preferably precipitated with hydrogen sulphide, and the copper sulphide so produced is then used to reduce the ferric salts in the copper'electrolyte, while an equivalent of copper goes into solution as the sulphate, which, in turn, is electrolyzed in the regular electrolyte to deposit the pure electrolytic metal with the simultaneous regeneration of an equivalent of acid.

The process will now be, described more in detail, reference being had to the accompanying drawing, which represents a flow sheet, or diagrammatic sketch, of the preferred method of carrying it out. The ore, j suitably crushed, is charged'into the leaching vats No. 1 and No. 2. The ore in vat No. 1 is supposed to be afresh charge, and that in No. 2 is supposed to have been treated with the regular, standard, or primary leaching solution,.but still containing some cX-' tractible copper in its sulphide combinations, and possibly also in some other combinations not easily extracted by the primary solution.

The primary solution may be considered as being a dilute acid solution containing relatively small amounts of ferric salts. This solution is applied to the fresh ore, as in vat No. 1. The copper solution, issuing from the leaching vat No. 1. and containing also considerable iron, mostly in the ferrous condition, flows into the copper depositing cells No. 1, which are preferably arranged in multiple, and the rate of flow thru the cells is'regulated in such a way that only from 0.10% to 0.25% of the. iron is oxidized to the ferric condition. The solution or electrolyte, on issuing from the copper cells No. 1 passes into the first reducing unit No.

1, where the ferric iron produced by the deposition of the copper in the first group of copper deposition cells, is reduced toithc ferrous condition, preferably by thensit of copper sulphide precipitated from the lean and foul solutions produced in another step of the process. The reducing unit will ordinarily. consist of an agitator in which the ferric iron is brought in intimate contact with the precipitated copper sulphide, a separator in which the copper sulphide precipitate is separated from the reduced solution, and a pump to return the settled sulphide sludge from the separator to the agitator. The reduction may be accomplished in a few minutes, especially if the solution is heated. The clear overflowing solution from the separator flows into the next set of copper depositing cells No. 2, where more copper is deposited and more ferrous iron oxidizing to the ferric condition, but this ferric iron, on account of the regulated rate of flow of the electrolyte, should not exceed 0.25%. On issuing from the copper depositing cells No. 2, the electrolyte flows into the reducing unit No. 2, and from the second reducing unit to the third set of copper depositing cells No. 3, and this is continued until the electrolyte is sufliciently impoverished in copper and regenerated in acid, after which it is againreturned to the ore to pass thru another cycle. The leaching of the ore in vat No. 1 is continued until the oxidized, or easily extractible, copper is brought into solution and removed; vat No. 1, wi 1 then be in the condition of vat No. 2. It is desirable to maintain theferric iron at not to exceed 0.25% on issuing from each set of deposition'cells, and to reduce this amount of ferric iron quickly and as completely as possible in the successive reducingunits. There will, of course, be no need of reducing the ferric iron in the last set of depositing cells, and hence a small amount of ferric iron will inevitably be in the primary leaching solution, and may be beneficial in the solution.

Manifestly, if this cycle of solution and deposition is continued indefinitely the iron in the primary solution, or electrolyte, Will accumulate in undesirable amounts, even tho the iron content may be maintained high;

When it is desired to eliminate some of the iron, or perhaps, to maintain the iron in the primary solution ata certain maximum, a small portion of the primary solution is diverted to form a secondary solution with which to extract the rcn'iainder qf-the copper in the ore after the application of the primary solution. This secondary solution is presumably high in iron. It is treated, preferably by electrolysis, to convert the iron in the ferric condition. This second ary solution then becomes an .active solvent of the copper, as in vat No. 2, in its sulphide cou'ibinations, and other combinations not readily soluble in dilute acid solutions.

This secondary leaching circuit will now be described. The regenerated ferric salt solution is applied to the leaching vat No. 2, Where it acts on the copper remaining after the applicatioi'i of the primary solution. On issuing (from the vat it will be rather low in copper andcontain most of the iron in the ferrous condition, altho some of the iron will In order to make 1 .ricsa'lts is reduced tothe ferrous condition Withthe simultaneous regeneration of an .equivalent ofiacid. The secondary solution,

now having the' salts of the variable valent elements reduced to their lowest valency, 1S

flowed into the H S precipitator,Where the zcopper is easily and completely precipitated from the reduced solution as the sulphide, with the simultaneous regeneration of more acid. Thev regenerated acid solution-now containing ferrous iron in solution and the I precipitated copper sulphide in suspension,

" is flowed into the copper sulphide separator,

Where the coppersulphide settles to the bottoni and the clear overflowing'solution passes on to theoxidizing cells in Which the reduced acid solution .is electrolyzed under oxidizing' conditions, to convert the'ferrous salts into the ferric salts. The oxidizing action of the electrolysis is Improved by agitation; it also assists in the depolarization, re

duces'the E. F. required in the electrol- *ysis,-and materially prolongs the life of the anodes. Compressed air for agitation may be introduced into the various cells as desired. Air also assists directly in the oxidiz ing action, but not energetically. If it is desiredto use a more energetic oxidizing agent than air in the conversion of the ferrous salts to'ferric salts, in the electrolysis, manganese dioxide may be used. Manganese dioxide is an effective oxidizer of the ter 9 roussalts, and may also act as a depolarizer.

If it is to lee-used as an oxidizing agent, it is preferably ground fine and introduced with the solutionsv into the oxidizing cells. The

air agitation prevents it from settling in the cells, and it flows out with the ferric solutions, into the separator, where it is se arated from the regenerated ferric'solutlon and again returned to the cells. The clear overflowing acid solution, now containing much of the iron in the ferric condition, is

returned to the ore in .v'at' No. 2,and the cycle repeated until the ,coppcris suficicntly ex;

tractcd. The ore is then Washed, and nece's 'sarily some o-f-the,solv'ent must be Wasted as in all leaching" processes, and the portion of, the solvent which is necessarily 'tvastcd willjust about keep the secondary solvent If it is deat a desired standard of iron. 1 sired to have a high iron-content 1n' the secondary solution, the ferrous sulphate from the hydrogen sulphide generator may be added to the solution- "The hydrogen sulphide may be generated but. for the purpose of" this process it is pre iron sulphide and dilute sulphuric acid;

.tate the copper chemically in a number of Ways,

reaction between cially if the solution is heated.

Within certain limits, the higher theiron in the secondary solution the more effective will be the oxidation and consequent depolaiy 1zat1on.- Itis notnicccssary to oxidize-all of the ferrous 110D. It lS'Pl'BfGlttblzllQttogdo so:

Supposethe secondaryleachingsolution con- If2.0% 115-31070 this" :ferric"condition' it. will ondary solution'during oxidizing electroly- SIS 13 not harmful, it is preferred to precipiand then electrolyze the secondary solution under highly. oxi dizing conditions. The copper deposited in the oxidizing cells would result in an impure metal, a very poor efiiciency at the cathode,

and a reduced efficiency at the anode. The ,copper sulphide precipitate, froin'the impure secondary solution, is quite pure and can be used effectively in the reduction of the ferric salts in the primary solution, and canin this way ultimately all be converted into thepure electrolytic metal While performing the very important function of re ducing the ferric salts and generation of acid.

It is preferred to heat the solution, especially in the secondary circuit, for the reason that sulphur dioxide reduction, as well as hydrogen sulphide precipitation, takes place more effectively in heated than in cold solutions, and the precipitate settles more rapidly, and in the oxidizingelectrolysis. oxidation is more readily effected and the do; polarization may be made practically coinplete under the conditions of this process.

While sulphur dioxide is preferred as a reducing agent, preparatory to precipitation with hydrogen sulphide, it is .not essential. Hydrogen sulphide will reduce the ferric. salts more effectively than sulphur dioxide. but there is more acid regenerated by the use of sulphur dioxide. There is no sulphur precipitated with sulphur dioxide reduction, and the copper sulphide precipitate with hydrogen sulphide is of a higher grade when the reduction is made with sulphur dioxide. Thcu, too, sulphur dioxide is a Waste gas in most copper metallurgical Works, and is rarely, if ever, as expensive as hydrogen sulphide.

Itis' desirable, in this process, to have V dation of the ferrous salts,'ar=d greatly im' imes the action of the ferric salts in the extraction of the copper from the ore, esp'eparatus such as that shown in posited.

It is notintended to draw a sharp line between the application of primary and secondary leaching solutions to the ore. As

' soon as the primary leaching is finished, it is preferred to follow it up innnediatelv with the econdary solution, and the operator will soon learn when to switch the issuing copper solution from the primary to the secondary circuit.

A. close separation need not he made between the copper sulphide. precipitate and the reduced regenerated acid secondary so-- lution. It is preferred to draw the copper sulphide precipitate from the bottom. of the separator as a thickened sludge and flow it into the agitators of the primary circuit.

The process may be carried out in any convenient apparatus. The leaching apparatus and copper deposition cells may he of any. standard design. For the reducing units, DOIT agitators and Dorr thickeners, or separators, are preferred. These sep araters are also preferred for separating the copper sulphide precipitate in. the secondary solution. For the sulphur dioxide reduction and hydrogen sulphide precipitation an apmy co-pending application Serial No. 16,962, filed March 2-5, 1915, (Patent No. 1,347,089) s preferred, and for the oxidizing electrolysis an apparatus such as that shown. in my (:0 pending applications Serial No. 145,88 hfiled February 1, 1917, (Patent No. 1,345? ,088) and Serial No. 231,534, filed April 29, 1918, (Patent No. 1,865,032) is preferred.

It is desirable to have a fairly violent.

agitation in the oxidizing cells, and this is possible when there is no copper to he dc In the presence of ferric salts, violent agitation, while it materially assists in the depolarization, also assists in redissolving the copper, if it is attempted to deposit copper while regenerating ferric salts. he sulphide precipitate, resulting from the precipitation of the copper in the secondary solution, with hydrogen sulphide, may be separated from the reduced and regenerated acid solution by flotation instead of by gravity, in a Dorr thickener. 'lhe sulphide precipitate is easily floated, and sometimes this method may be preferred. If preferred, the C118 separator may be represented by any of the well known flotation machines.

Lead, ferrosilicon. or magnetite anodes will ordinarily be used to deposit the copper from the primary solution. Carbon anodes will ordinarily he used in clectrolyzing the secondary solution there will he no difficulty in maintaining good depolarization of the carbon anodes in a sulphate solution high in ferrous iron, under the conditions of agitation and elevated temperature of the electrolyte as contemplated in the operation of this step of the process.

The process has been described in connection with sulphate solutions; it is equally applicable with chloride solutions.

I claim:

1. A process of extracting copper from its ores, which consists in first treating the ore with an acid solution relatively low in ferric iron to extract a portion of the copper, and then treating the ore with an acid solution relatively high in ferric iron to extract the remainder of the copper, and separately precipitating the copper from both solutions.-

2. A process of extracting copper from its ores, which consists in first treating the orc with an acid solution relatively low in. ferric iron to extract a portion of the copper, and then treating the ore with an acid solution relatively high in ferric iron to extract the remainder of the copper, precipitating the co r from. the first solution electrolyticall .nd precipitating the copper from. the second solution chemically.

3. A process of extracting copper from its ores which consists, inlirst treating the ore with an acid solution to extract a portion of the copper, and then treating the ore with an acid solution containing ferric iron to ext'act the remainder of the copper, prccipi-' tating the copper in the first solution electrolytically, precipitating the copper in the second solution chemically, and treating the first solution with the chemically precipitated copper from the second solution. I

4-. A process of extracting copper from its 0 es containing the copper in its oxide and sulphide con'ibinations which consists, in first treating the ore with an acid solution to extract the copper in its oxide combinations, then treating the ore with a solution contaming ferric iron to extract the copper in its sulphide combinations, and separately the copper from both solutions.

5. A process of extracting copper from its ores which consists, in treating the ore with a primary acid solution to extract a portion a of the copper, then treating the ore with a secondary solution containing ferric iron to extract the remainder of the copper, precipitating the copper from both solutions separately, and separately returning both solutions to the ore.

6. A process of extracting copper from its ores which consists, in treating the ore with a primary acid solution to extract a portion of the copper, then treating the ore ivith a secondary solution containing ferric iron to extract the remainder of the copper, electrolytically precipitating the copper from the primary solution, and chemically precipitating the copper from the secondary solution, and separately returning both solutions to the ore.

7. A process of extracting copper from its ores which consists, in treating the ore with a primary acid solution to extract a. portion of the copper, then treating the ore with a n Secondary solutioii conta' ling ferric iron to fextr act the remainder of the copper, elec- I trolytically precipitating the coppertrom the primary solution, chemically precipitatlng the copper from the secondary solution,

' :separately returning both solutions to the 0rd,; and treating the ,primary solution with the precipitate obtained from the secondary trolytically precipitating the copper. from.

i the primary solution, chemically precipitating the copper from the secondary solution,

electrolyzing the secondary solution tocon vert, the ferrous iron tothe fcrriccondition,

' and returning both solutions separately to the ore. A I

y 9. A process of extracting copper-from its ores which consists, in treating the ore Wltll' apr mary'acid solution to-extract a P01151011 of the copper, then treating the ore with a secondary acid solution containing ferric iron to extract the remaindero'f the copper, electrolytically precipitating the copper from the primary solution,- chemieally precipitating the copper from the secondarysolution as the sulphide, electrolyzing the secondary solution to convert *the ferrous 'iron in the solution to the ferric condition,

, separately returning both the primary and secondary solutions to the ore. andjtreating the primary solution during the electrolytic precipitation with the sulphide precipitate y from the secondary solution.

10. A process of extracting copper from itso'res which consists, in treating the ore with a primary acid solution containing iron salts to extract a portion of the copper, electrol'yzing the resulting solution to deposit thevcopper, diverting enough of the primary solution as it becomes .undesiral'ily charged jw'itlniron o fm in a secondary solution, elecnlyzing puc secondary solution to convert the ferrous iron to the ferric condition, and ,th'e napplying the regenerated ferric solu- .tion to the ore to extract the ren'iainder of the copper.

l1. Agprocess of extracting copper from its ores \vhich eon sis n treating the, ore with an acid solutionto" extract a portion of the copper electrolyzing the resulting copper solutioncontainin'g salts of iron to deposit the copper and regenerate acid in such awayas to prevent the accumulation of ferric iron in the electrolyte, and then electrolyzing the solution in such a Way as to promote the formation and accumula tion of the ferric iron, and then applying the regeneratedferric iron solution, o, the ore to dissolvethc remainder otthecopper,

from its i ric salt solution to the ore 12. A process of treatingores o-iimetals which consists, in treating the orejfwith an acid solution to extract a portionof the metals, .electrolyzing the resulting metal solution containing salts of iron I to; deposit the metals in such a Way as to retard the;,for-- mation. and accumulation v otfcrric iron in the electrolyte, and then electrolyzi'ng the solution in such a way as to promote the formation and accumulation of the ferric iron, and. then applyingtl'ie" regenerated fer-- to extract the remainder ofthe metals. i

13. A process of extracting copper from its ores which consists, in treating the ore With'an acid solution to dissolve the copper,

'eleetrolyzing ,the resulting copper solution containing salts. of iron to deposit the, copper and subjecting the electrolyte tothe. ac-

tion of a. reducing agent, andthen. after gther electrolyte is sufficiently impoverished ,in

copper and regenerated in acid elficlgrolyzing 1t again and suluectmg it to the actionof an oxidizing'agent; 1

14. A process of extracting 66 3 55355111: I

its ores which consists, in treatin'gtheuore wlth a primary acid solution to extract a portion of the copper, electrolyzingJthe-solution to deposit the copper, diverting 'e'nouglrof the primary solution to form a: secondary solution and in such-a ivayias to prevent an undesirable excess of ironsalts in the primary solution, treati.ng 'the sec ondarysolution to convert the iron from the ferrous to the ferric condition, applying.

the secondary ferric solution to-the oreto extract theremainder of the copper, and

chemically precipitatin secondary solution. a r,

15. A process of extracting copper-from; its ores which consists in part of maintaining separate a-primaryv and a secondary isolution'circuitstand passing the excess, ofiron 9; the copper in the salts in the primary circuit to thesecondary circuit,- electrolyzing their-on salt solution, in the' secondary circuit underoxidiz ng conditlons to convert the iron into the ferric condition, and then applying theferric. iron solution so obtained to extract copper from the ore 1n=1tssulph1de combinations; i

16. In the'treatment of copper ores in which a portion of the copper is soluble in dilute acid and-another portion soluble, in

a solution of ferric'salts, the process comprising :sulojectingv the ore successively to the actionof a. primary solvent relatiyely low-in ferric iron-to extract the readily soluble copper and then to the action of a. solventrelatively high in ferric iron to extract theeopper not readily soluble in the primary solution.

17. A process of extracting copper from its ores which consists in part of subjecting the ore successively to the action of a pri-- tard the formation and accumulation of for- .ric iron, and then when the solution be- Comes undesirably charged with iron salts diverting a portion 0f the solution and electrolyzing the diverted portion to pro mote the formation and accumulation of ferric iron, and then applying the resulting ferric salt solution to the ore.

19. A metallurgical process which con sists in treating ores of metals with a solvent for the metals, electrolyzing the resulting metal solution to deposit the dissolved metal values and regenerate the solvent, repeating the cycle until the solution becomes stifliciently charged with impurities, then di vcrting a portion of the solution and chemically precipitating the remaining metal values-- from the diverted foul solution, and then applying the-barren foul solution to the ore.

20. A metallurgical process which consists in treating ores of metals with a solvent for the metals, electrolyzing the resulting metal solution to deposit the dissolved metal values and regenerate the solvent, repeating the cycle until the solution becomes sufiiciently charged with impurities, then divcrting a portion of the solution and chemically precipitating the remaining metal values from the diverted foul solution, electrolyzing the diverted foul solution freed from its metal values, and then applying the electrolyzed barren solution to the ore.

21. A metallurgical process by which ores of copper are treated with a primary acid solution to extract a portion of the copper and a secondary solution high in iron salts to extract the remainder of the copper, the steps which consist in chemically precipitating the copper from the secondarysolution, separating the chemical precipitate from the resulting solution, and then treating the primary solution with the chemical precipitate from the secondary solution.

22. A metallurgical process by which ores of copper are treated with a primary s0lution to extract a' portion of the copper and a secondary Solution containing salts of iron to extract the remainder of the copper, the steps comprising electrolytically precipitating the copper from the primary solution, chemically precipitating the copper from the secondary solution, separating the resulting chemical precipitate from the secondary solution, electrolyzing the barren secondary solution, and returning the electrolyzed ore.

23. A process of treating ores of copper comprising leaching the ore witli'a dilute acid solution to extract a portion of the copper, alternately electrolyzing and reduci ng the resulting copper solution containing salts of iron to deposit the copper and regenerate acid until the solution is sufficiently depleted lII COPPGI and regenerated in acid, then returning a portion ofthe regenerated acid solution to the ore and chemically precipitating the remaining copper from another portion, electrolyzing the resulting solution from which the copper has been chemically precipitated to regenerate ferric salts, and then returning the resulting ferric salt solution to the ore to extract another portion of the copper.

24. A process of treating ores of copper, comprising leaching the ore with an acid solution containing salts of iron to extract a portion of the copper, precipitating a portion of the copper electrolytically with the barren solution containing ferric iron to the simultaneous regeneration of acid, then pre;

cipitating a portion of the copper chemically with the regeneration of more acid, then treating the solution from which the copper has been chemically preci itated to convert the ferrous salts into the erric condition, and then returning the regenerated ferric salt solution to the ore.

25. A process of treating copper ores, comprising leaching the ore with an acid. solution containing salts of iron to extract a portion of the copper, precipitating a portionof the copper from the solution electrolytically with the simultaneous regeneration of acid, precipitating a portion of the copper chemically with the simultaneous regeneration of more acid, then electrolyzing the resulting solution depleted in copper and agitating the electrolyte with air to con vert the ferrous iron in the solution into the ferric condition, and then returning the regenerated acid ferric salt solution to the ore to dissolve more copper.

26. A process of treating copper ores, comprising leaching the ore with a solvent containing salts of iron to extract a portion of the copper, chemicallyprecipitating the copper from the solution so that the solution will beugractically free from copper, then electrol Zllig the resulting solution to convert the errous iron into the ferric condition and agitating the electrolyte during electrolysis, and then returning? the regenerated ferric salt solution toth'e ore to extract morecopper. Q

'27. A process of treating ores of metals comprising, leaching the ore with a primary solutioirrelatively low in ferric salts to ex:

tract a portion of the metals, then leaching naeaaoe the ore with a secondary solution relatively secondary solution, applying the precipitate from the secondary solution to the primary solution, and then electrolyzing' the primary solution to'deposit the metals.

28. A process comprising, treating ores of metals with a primary solution relatively low in ferric salts to extract a portion of the metals, then treating the ore with a solution rclativelyhigh in ferric salts to extract the remaining metals, precipitating the metals from the secondary solution and returning the secondary solution to the ore, applying the recipitate fromthe secondary solution to the primary solution, then'electrolyzing the primary solution to deposit the metals and regenerate the solvent and returning the regenerated primary solution to the ore.

29. In the treatment of copper ores in which a ortion of the copper is soluble in dilute acld and another portion solublein a ferric salt solution, the process comprising subjecting the ore successively to the-action of a primary solvent relatively low in ferric ir n to extract the readily soluble copper and then to the action of a secondary solvent relatively high in ferric iron to extract the copper not readily soluble in the primary solution, electrolytically precipitating the copper from the primary solution, chemically precipitating the co per from the secondary solution, then e ectrolyzing the secondary solution with carbon anodes, and returning the electrolyzed solution to the ore. t n

30. Inthe treatment of copper ores in which a portion of the copper is soluble in dilute acid and another portion soluble in a ferric salt solution, the process comprising subjecting the ore successively to the action of a primary solvent relatively low in ferric iron to extract the readily soluble copper and then to the action of a secondary solvent relatively high in ferric iron to extract the copper-not readily soluble in the primary solution, precipitating the copper from the primary solution-by electrolysis, precipitating the copper from the secondary solution with hydrogen sulphide generated from Ten rous sulphide and acid, adding the resulting ferrous salt from the generation of hydrogen sulphide to the secondary solution, treating the secondarv solution to convert the ferrous iron to the ferric iron, and returning the,

solution to the ore.

31.111 ,the treatment of copper ores in which a portion of the copper is soluble in dilute acid and another portion soluble in a ferric salt solution, the process comprising subjecting the ore successively to the action of a primary solution relatively low in ferric iron to extract the readily soluble copper and then to the action of a secondary solu tion relatively high in ferric iron to extract the copper not readily soluble in the primary. solution, precipitating the copper from'the primary solution separatelyv from the secondary solution, chemically precipitating the copper'from the secondary solution,.then electrolyzing the secondary solution in the presence of a substance other than air which is capable of promotingthe production of ferric salts, and returning the electrolyzed solution to the ore.

WILLIAM E. GREENAWALT. 

